The Apollo Experience Report: Thermal Protection Subsystem explains that there are three sections to the Apollo heat shield:

  • The aft heat shield, at the "base" of the cone and adjacent to the SM. This is probably what you think of when you hear "heat shield".

  • The crew compartment heat shield, on the "sides" of the cone. It covered the main hatch and has many openings for windows, RCS engines, antennas, and vents.

  • The forward heat shield, at the "tip" of the cone. It covered the docking tunnel.

Apollo heat shields

All three heat shields were made of a fiberglass honeycomb filled with epoxy.

The forward heat shield was automatically ejected at 24,000 feet by a baroswitch (with manual backup switches). It had its own parachute, landed separately from the CM, and had its own recovery helicopter. The other two heat shields remained attached to the CM. The drogue, pilot, and main parachutes were completely separate from the heat shield chute, and began their deployment sequence two seconds after 24,000 feet.

Where are the forward heat shields today? Are they with their respective command modules? Were some lost to the ocean? In some government warehouse next to the Ark of the Covenant? I can only account for Apollo 15's, which was extensively examined as a possible cause of the failure of one main parachute on that flight.

  • $\begingroup$ The heat shield is made from stainless steel panels and a fiber-glas honeycomb bonded with adhesive tape. The ablative material selected for the TPS is designated Avco 5026-39G and consists of an epoxy-novalac resin reinforced with quartz fibers and phenolic microballoons. $\endgroup$ – Uwe Jun 18 at 13:55
  • $\begingroup$ @Uwe: Very good, but how does that answer the question? $\endgroup$ – DrSheldon Jun 18 at 14:11
  • $\begingroup$ It does not answer the question, but the honeycomb was not made from stainless steel. Using a thermal isolator like fiber-glas was a better choice for the heat shield. $\endgroup$ – Uwe Jun 18 at 14:20
  • $\begingroup$ @Uwe: Thanks. Confirmed by tech note D-7564, and the question corrected. $\endgroup$ – DrSheldon Jun 18 at 14:28
  • $\begingroup$ My guess is all forward heat shields are lost in the huge ocean far away from the splash down points of the Apollo capsules. Locating them on the deep sea floor using sonar would be very expensive and difficult. They may be hidden under a thick layer of sediments from more than five decades. $\endgroup$ – Uwe Jun 18 at 20:09

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